This invention relates to a technique for semiconductor devices and more particularly, to a technique effective for application to semiconductor devices having power MISFET (metal insulator semiconductor field effect transistor).
Transistors for high-power purposes dealing with electric power of several watts (W) or over a recalled power transistor, and various types of structures have been studied.
Among them, power MISFET includes ones called a longitudinal type and a transverse type and are classified into a trench-type structure and a planar structure depending on the structure of a gate portion.
Such power MISFET has a multitude of (e.g. several tens of thousands of) MISFET's in fine pattern connected in parallel in order to obtain high power.
For instance, Japanese Unexamined Patent Publication No. Hei 7 (1995)-249770 discloses power MISFET of the trench gate type.